Various types of enzymes are known in the art as additives for detergent compositions. For example, detergent compositions containing proteases, lipases, amylases and cellulases and various combinations thereof have been described in the literature and several such products are currently on the market. Of these enzymes, proteases, lipases and amylases are most abundantly used. The enzymes assist in the cleaning of fabrics by degrading their natural substrates protein, fat and starch. Cellulase, on the other hand, is not added to detergent products because of its capability to break down cellulose, but rather to attain certain "care" benefits such as colour clarification, anti-pilling and reduction of the harshness of the fabric.
The harshness-reducing action of cellulase in detergent compositions was first described GB-A-1 368 599 (Unilever). DE-A-3 207 847 (Kao) discloses that the addition of cellulase to a detergent product improves its cleaning performance. EP-A-220 016 (Novo Nordisk) describes a colour clarification activity of cellulases.
Cellulases occur in nature as very complex mixtures of enzymes and in recent years several attempt have been described to isolate its various components and to produce them by means of recombinant DNA techniques. For a classification of cellulases, see Henrissat and Bairoch, Biochemical Journal 293, 781-788 (1993). A special class of cellulases, the endoglucanases, have been described as particularly useful for detergent applications.
W-A-89/09259 (Novo Nordisk) discloses a cellulase preparation useful for reducing the harshness of cotton-containing fabrics, comprising at least 40% of an endoglucanase component with a high endoase activity and affinity towards cellulose. W-A-91/17243 (Novo Nordisk) discloses a cellulase preparation consisting essentially of a homogeneous endoglucanase which is immunoreactive with or homologous to a 43 kD endoglucanase derived from Humicola insolens DSM 1800. The pH optimum of the endoglucanase from Humicola insolens DSM 1800 is about 8. W-A-94/21801 (Genencor) discloses the production and purification of endoglucanase EGIII from Trichoderma longibrachiatum. This endoglucanase is said to have a pH optimum of 5.5-6.0.
W-A-95/24471 (Novo Nordisk) discloses that certain cellulases of Family 7 (in the classification according to Henrissat), which do not comprise a carbohydrate binding domain, may have enhanced activity which may result in improved soil removal from fabrics.
Thus, although various endoglucanases have been reported to have favourable properties in detergent products, there is still a need to provide alternative or improved endoglucanase containing detergent compositions. In particular, the storage stability of endoglucanases, as well as their stability in the presence of proteolytic enzymes and/or bleach leave to be desired, especially in liquid detergent formulations. There is also a need for detergent products having improved anti-pilling properties.
For instance, it was found that the activity of the of Endoglucanase III from Trichoderma longibrachiatum, which has a pH optimum of 5.5-6.0, is rapidly decreasing in the alkaline region. Thus, there is also a particular need for endoglucanase containing detergent compositions which exhibit typical cellulase-associated benefits at alkaline pH.
It is therefor an object of the present invention to provide a detergent composition for fabric washing, containing an endoglucanase that is stable in (liquid) detergents during storage, in particular in the presence of proteolytic enzymes and/or bleach. It is a further object of the present invention to provide a detergent composition containing an endoglucanase that has satisfactory anti-pilling properties and that is effective at alkaline pH.
We have now surprisingly found that these and other objects can be achieved by using in the composition an endoglucanase which contains no cellulose binding domain and wherein the catalytic domain contains at least two and preferably tree, four, five or even more disulphide bridges.
In particular, such endoglucanases can be used to formulate detergent compositions which are stable and exhibit anti-pilling and colour clarification properties, even at alkaline pH and in the presence of proteolytic enzyme and/or bleach. We have also found that such endoglucanases do not depend on special proteases for stability, such as described in W-A-92/18599 (Novo Nordisk) for the 43 kD endoglucanase derived from Humicola insolens DSM 1800.